1. Technical Field
The present invention relates to compressed air systems. In particular, the present invention relates to an air compressor that uses lubricating oil and to a method and apparatus for reducing migration of oil from the compressor to the compressed air output.
2. Description of the Prior Art
Air compressors using lubricating oil are commonly used in, for example, air brake systems of heavy vehicles. The compressor uses engine oil or another oil for internal lubrication. Some of this oil can undesirably migrate to the air brake system via the compressed air output of the compressor, a result sometimes referred to as oil-passing or oil carry-over. For example, in one known compressor, when the compressor is in the unloaded mode, the swept volume of the cylinder is open to a small chamber in the head of the compressor where air is compressed and expanded. Oil collects in this chamber, or drains back down into the cylinder and is carried into the air stream when the compressor loads.